1. Technical Field
This invention relates generally to internal combustion engines, and more particularly to pistons and their method of construction.
2. Related Art
Engine manufacturers are encountering increasing demands to improve engine efficiencies and performance, including, but not limited to, improving fuel economy, improving fuel combustion, reducing oil consumption, and increasing the exhaust temperature for subsequent use of the heat within the vehicle. In order to achieve these goals, the engine running temperature in the combustion chamber needs to be increased. However, while desirable to increase the temperature within the combustion chamber, it remains necessary to maintain the piston at a workable temperature. By keeping the piston at a workable temperature in the combustion chamber, the onset of carbon build-up on the upper land of the piston is controlled, which in turn improves the running efficiency of the engine. As such, although believed desirable to increase the temperature in the combustion chamber, there is a tradeoff in that increasing the combustion chamber temperature can result in increase of overall temperature of the piston, particularly in the upper land region.
Some attempts have been made to construct pistons having an ability to increase the combustion chamber running temperature. One known attempt uses a ceramic coating on an underlying metal piston. However, these pistons typically experience strength, durability and processing issues making them unsuitable for use. Other attempts include using moderate stainless steel having a chromium content between 4-6% and a thermal conductivity of about 33 W/m-K, and although useful to an extent, these efforts have not provided the necessary reduction in thermal conductivity to achieve and sustain the increased running temperatures desired.
A piston constructed in accordance with this invention overcomes the disadvantages of known piston constructions, including those associated with ceramic coated pistons. As such, a piston constructed in accordance with this invention facilitates increasing the combustion chamber temperature, thereby providing enhanced running efficiencies, while having high strength and durability and also inhibiting the potential for carbon build-up.